I. Technical Field
The present invention relates generally to wells, and more particularly to methods and apparatuses that optimize oil and gas wells.
II. Background Discussion
Oil and gas wells are ubiquitous in the petrochemical industry. At various stages in the life of a well, the quantity and/or quality of production may change over time. Early in the life of a gas producing well, sometimes referred to as the “initial production” stage, there may be plenty of downhole pressure and the gas produced from the well may be substantially dry such that there is little need to separate the gas from liquids such as oil and water.
In the next stage of a gas producing well, sometimes referred to as the “early liquid loading” stage, the downhole pressure may decline from the initial production stage and the well may begin to produce liquids, such as oil and water, in a mist form along with the gas. Gradually, this liquid in the well may build up to a point where the amount of liquid in the well, sometimes referred to as the “liquid load”, is such that it overcomes the downhole pressure in the well and the well ceases production. In an attempt to prevent the well from loading up with liquids to the point that the well ceases production, gas may be produced intermittently from the well by opening and closing a valve in the gas production line (sometimes referred to as “shutting in” the well). The idea being that shutting in the well for a period of time may allow a sufficient downhole pressure to build up and overcome the liquid load in the well. Also, in an attempt to prevent the well from loading up with liquids, a plunger-type lift system may be implemented in the well, such that when the well is reopened, the built up downhole pressure may use the plunger to lift the fluid from the well.
Some conventional approaches attempt to maximize gas production during the early liquid loading stage by timing the well to be off for a certain period of time. In some cases, the period of time during which the well is shut in for is adjusted by the well's operator based upon the operator's familiarity with that particular well's characteristics. While timing the well to be off for a period of time may aid in optimizing well production during the early liquid loading stage, this optimization may rely too heavily on the skill of the well operator in adjusting this period of time.
Also, some conventional approaches attempt to maximize gas production during the early liquid loading stage by shutting the well “in” based upon the speed at which the plunger moves within the well. The idea being that, after the well is “shut in” for a sufficiently long period of time to build up downhole pressure, the plunger will be at the bottom of the well and travel to the top at substantially the same speed as the liquid being cleared from the well. For example, many conventional approaches control the frequency and duration of well shut in such that the plunger speed is in the range of 600-700 feet per minute. Unfortunately, if the plunger never reaches the bottom of the well during the shut in period, then the calculated plunger speed calculation may be inaccurate causing this well optimization scheme to be inaccurate.
In the final stage of production, sometimes referred to as the “mature” stage, the gas produced includes a greater amount of liquids and the overall downhole pressure continues to decline. Because the characteristics of the well may change drastically during the mature stage of production as compared to the early liquid loading stage, the time period that the well is shut in order to optimize production is different during the mature stage than it is for early liquid loading stage. In fact, the time period that the well is to be off in order to optimize well production may vary from cycle to cycle during the mature production stage. Thus, the well operator's familiarity with the well and past practices of shutting it in for optimum production may no longer apply during the mature stage of production. Furthermore, the liquid loading in the well may be so great during the mature stage that the plunger either floats on the liquid column in the well or stalls when the well is turned on if the well is not opened under the right conditions.
Accordingly, methods and apparatuses that optimize an oil and gas well while overcoming one or more of the aforementioned problems are desirable.